Educational program for intraoperative transesophageal echocardiography

A plunger pump is provided which comprises: a pump body having a cylinder hole with an expanded diameter section; a plunger defining, together with the lid member, a pump chamber; and a coiled spring disposed within the expanded diameter section. The coiled spring includes: an effective winding section; a lid-side seat winding section; and a plunger-side seat winding section. The lid-side seat winding section has an outer diameter larger than an outer diameter of the effective winding section, and the plunger-side seat winding section has an outer diameter smaller than an outer diameter of the plunger. With this configuration, the coiled spring within the pump chamber can have increased stability, and can be located in the center of the pump chamber.